fix: add case for update till root

bpt/include/bpt/bpt.hpp

@@ -410,6 +410,17 @@ class BPlusTreeIndexer {
     RemoveEntryInRightSkewPath(pos);
     return;
   }
+  void TryUpdateTillRoot(PositionSignType &pos) {
+    if (pos.path.size() < 2) return;
+    BasicPageGuard &page_guard = pos.path.back().first;
+    if (pos.path.back().second != page_guard.template As<PageType>()->data.key_count - 1) return;
+    BasicPageGuard &parent_page_guard = pos.path[pos.path.size() - 2].first;
+    if (pos.path[pos.path.size() - 2].second >= parent_page_guard.template As<PageType>()->data.key_count) return;
+    parent_page_guard.template AsMut<PageType>()->data.p_data[pos.path[pos.path.size() - 2].second].first =
+        page_guard.template As<PageType>()->data.p_data[page_guard.template As<PageType>()->data.key_count - 1].first;
+    pos.path.pop_back();
+    TryUpdateTillRoot(pos);
+  }
   void RemoveEntryAt(PositionSignType &pos, bool is_fixing_up_recursive = false) {
     if (siz == 1) {
       // special case for the last entry
@@ -429,10 +440,16 @@ class BPlusTreeIndexer {
         page_guard.template As<PageType>()->data.p_data + pos.path.back().second + 1,
         (page_guard.template As<PageType>()->data.key_count - pos.path.back().second - 1) * sizeof(key_index_pair_t));
     page_guard.template AsMut<PageType>()->data.key_count--;
+    bool need_update = false;
     if (pos.path.size() >= 2 && page_guard.template AsMut<PageType>()->data.key_count == pos.path.back().second) {
       auto &parent_page_guard = pos.path[pos.path.size() - 2].first;
-      parent_page_guard.template AsMut<PageType>()->data.p_data[pos.path[pos.path.size() - 2].second].first =
-          page_guard.template As<PageType>()->data.p_data[page_guard.template As<PageType>()->data.key_count - 1].first;
+      if (pos.path[pos.path.size() - 2].second < parent_page_guard.template As<PageType>()->data.key_count) {
+        parent_page_guard.template AsMut<PageType>()->data.p_data[pos.path[pos.path.size() - 2].second].first =
+            page_guard.template As<PageType>()
+                ->data.p_data[page_guard.template As<PageType>()->data.key_count - 1]
+                .first;
+        need_update = true;
+      }
     }
     if (has_enough_keys) {
       if (page_guard.template As<PageType>()->data.page_status & PageStatusType::ROOT &&
@@ -444,7 +461,11 @@ class BPlusTreeIndexer {
         page_id_t page_to_delete = page_guard.PageId();
         pos.path.clear();  // all page_guards are invalid now
         bpm->DeletePage(page_to_delete);
-        return;
+      }
+      if (need_update) {
+        // now we need to check if we have to update the right bound till the root
+        pos.path.pop_back();
+        TryUpdateTillRoot(pos);
       }
       return;
     }

design.md

@@ -23,6 +23,7 @@
 - p[i]子树中的所有key K都满足： k[i-1] \< K \<= k[i]，且k[i]一定能取到，即直接无缝对接lower_bound
 - 对外接口提供类似于迭代器的东西，但该迭代器只支持向后单项移动、读取value值、修改value值，并且，迭代器会保留PageGuard，因此如果B+树在迭代器之前析构，会出现访问越界。
 - 由于子区间**左开右闭**，于是绝大多数Internal Page和Leaf Page一样，都没有尾后指针，整棵树的左下角会有一大片的leaf like pages，它们都有个共同特性，即指针数量和键值数量相同，但真正的leaf page还需要额外维护page状态标号和p_n指针。
+- 当删除时，有一定可能在leaf like区域触发一路更新到树根的操作
 
 # UI设计
 - 语言：Python

test/t1_mk.cpp

@@ -21,8 +21,8 @@ int main(int argc, char *argv[]) {
   fprintf(fout, "Seed = %u\n", RndSeed);
   fclose(fout);
   // ======================================
-  int n = 1000;
-  int total_keys = 300;
+  int n = 100000;
+  int total_keys = 30000;
   set<string> keys_set;
   for (int i = 0; i < total_keys; i++) {
     string key = "#" + to_string(rnd_less(1000000)) + "#";
@@ -36,7 +36,7 @@ int main(int argc, char *argv[]) {
   cout << n << endl;
   for (int i = 0; i < n; i++) {
     int tmp = rnd() % 10;
-    if (tmp <= 4) {
+    if (tmp <= 3) {
       string key = keys_vec[rnd_less(keys_vec.size())];
       int val = rnd_less(1000000);
       cout << "insert " << key << " " << val << "\n";
@@ -46,7 +46,7 @@ int main(int argc, char *argv[]) {
     } else if (tmp <= 6) {
       string key = keys_vec[rnd_less(keys_vec.size())];
       int val = rnd_less(1000000);
-      if (rnd() % 2 == 0 && mp[key].size() > 0) {
+      if (rnd() % 4 > 0 && mp[key].size() > 0) {
         // 选择一个有意义的删除项
         val = mp[key][rnd_less(mp[key].size())];
       }